Pretensioners are used to rapidly pull in slack in a seatbelt at the onset of a crash to more securely restrain the vehicle occupant against forward movement and potential injury by collision with the internal structure of the vehicle. In addition, the pretensioning operation pulls the occupant into, or at least towards, the correct seating position to maximize the effect of a second restraint such as an airbag.
A modern seatbelt is known as a 3-point restraint because it is secured to the vehicle at three points arranged about the occupant so as to provide a diagonal torso section and a horizontal lap portion to hold the vehicle occupant in the seat. The seatbelt is attached to the vehicle by a spring-loaded retractor tending to pull in the seatbelt, and by a buckle for quick release of the seatbelt.
Pretensioners can be located at the retractor or at the buckle end of the seatbelt. The present invention relates particularly to a buckle end pretensioner and aims to provide an improved pretensioner.